Switch is a line connection device that transfers a locomotive from one line to another and is widely used in railway, mine road. Pass-through capability of a line can be fully exploited with the help of switch. Switch is a huge family, the most common one is ordinary single switch, which is composed of three units: converter, connecter, frog and guard rail. The converter comprises basic rail, point rail and converter mechanism. Besides single switch, there are also double switch, triple switch and multiple switch (multiple cross switch) and so on. The switch has features such as large number (number of switches in a station larger than medium size often approaches thousands of groups, for example), complicated structure, short service life, high failure frequency, high maintenance cost etc.
Switch failure is divided into indoor failure and outdoor failure, the former is primarily the failure of motor per se and the latter is the failure while the switch is pulled or in use. Generally, since switch device is exposed at outdoor for a long period of time, it is frequently interfered by outside factors and its rate of failure is much higher than that of indoor switch.
Switch failure will bring severe property loss and human casualty; however, it is very difficult to accurately estimate and predict a switch failure in practice, it is thus difficult to take measures to prevent an accident from happening before a switch failure. Human maintenance and inspection on switch is manpower consuming, and often it is difficult to be conducted in day time due to time limit.